GE Merlin: Fact of Fiction?

GE Merlin: Fact of Fiction?
Posted in: Reverse Osmosis
One of the most popular products in the water treatment business is the GE Merlin 700 Gallon Per Day Reverse Osmosis System.  It delivers nearly a half gallon a minute under idealconditions.  Consumers hear that it is "tankless" and assume it is better than other "tank-type" RO's and is the latest and greatest in reverse osmosis technology.  While it is an amazing piece of equipment, it does have issues.  First of all, let's talk about its' good points.
  1. It makes lots of water and does it economically, so if you brew beer, do reef-keeping, have a salt water aquarium, greenhouse of do hydroponics, the Merlin is hard to beat, especially if you need hundreds of gallons of water a day.
  2. The more you use a Merlin, the better the water is.
  3. The initial cost is very low and it is downright impossible to find any reverse osmosis system that can produce this much water at such a low price.
Now, the drawbacks of a Merlin:
  1. If you use only a few gallons of water a day, the odds are that the water quality will be wretched unless you use a "flush tank," because of TDS Creep.  The flush tank surrounds the GE Merlin Membranes with RO water to prevent the TDS creep, but it also causes the Merlin to use a lot more water (it will waste 4-5 gallons each time it fills the flush tank, which is every time you turn on the faucet - If you get a drink 10 times a day, you will waste about 50 gallons of water for those 10 glasses!).
  2. The Merlin has problems shutting off.  In other words, after you have stopped using water, and the Merlin should shut-down, it doesn't!  Instead, it just runs to drain and may waste hundreds of gallons of water a day.  We have an inordinate amount of Merlins that are sent back because of this.
  3. It sounds like a "freight train" when it is making water!
Here's an actual case study with a GE Merlin.  We installed a GE Merlin under the kitchen sink for a man in Brownsburg, Indiana, which has a TDS (total dissolved solids) level of 520.  He kept complaining of "cloudy ice cubes."  So, we went to his home after the RO had sat unused all day.  We tested the first glass of water and it was 415 PPM.  Here are the rest of the results:
  • After 1 minute -   346 PPM
  • After 2 minutes - 278 PPM
  • After 3 Minutes - 191 PPM
  • After 4 Minutes -   96 PPM
  • After 5 Minutes -   19 PPM (Pretty good water, but who wants to wait 5 minutes for a glass?)
Now, this could be solved by a "flush tank," but in this case, the homeowner said "Why do that?"  So, we put in a permeate pump RO system (which delivers the same amount of pressure out the faucet as you have coming in), which always delivers less than 20 PPM, with better pressure and much less waste water.  Another thing to think about is that the GE Merlin Membranes cost about $200.00 to replace, while you can buy a membrane for the permeate pump RO for less than $30.00.
  • More Pressure
  • Less Waste
  • Better Water Quality
  • Lower Operational Costs
What's not to like?  That's why I have a (non-electric) permeate pump RO in my house. Now, we also find out that GE or Pentair is going to discontinue the Merlin and introduce a new and improved Merlin.  Yes, product failure is part of the reason they are introducing it, but the main reason is that they want to eliminate Internet sales of this product and are only going to give it to a limited number of distributors, who won't sell it on the WEB.  They want to line their distributors pockets with money while sticking it to the consumer... again! Necessity is the mother of Invention.  Watch and see why this will be a mistake for Pentair.
November 11, 2009
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September 1, 2010 at 3:59 PM
Hello and a massive thanks to the Water Doc for the info on Merlin. This is what us consumers need more of the Truth!!! My first ro was a Merlin and I ditched it after a few months due to problems such as high TDS now thanks to you I know why. I have since invested a load of money in trying many different RO's and they are not without fault. Many issues with the 4 way shut off valve not working and also water constantly running down the waste pipe with now way to tell or warn the client. I now have my eye on a tankless RO system Compact 400gpd from Taiwan it is pricey but I like the idea of no tank to avoid bacteria buildup the downside is that it is powered by a powerful pump in order to get enough faucet flow. The upside is that it is a push and screw system which is very easy for my clients to change. If you have any views on this system please do let me know. Gratefully David
September 8, 2010 at 1:01 PM
Hi Mark and David, I enjoyed reading your posts. I'm in the market for my first RO system and was all set to buy the Melin until I read your posts.... Mark, do you have any update on the "new and improved Merlin" that is mentioned in your post, e.g. when will it be available and what are the improvements? David, can you direct me to any information regarding the tankless RO system from Taiwan, e.g. specs, reviews, brochures, where to purchase etc. Your comments will be greatly appreciated. Thanks Robert
September 19, 2010 at 11:55 AM
Robert & David, I wouldn't hold my breath on the new and improved Merlin. Here's the basic problem: When you have a "tankless" Reverse Osmosis System, you obviously have to have very large membranes. Two problems with large membranes are: 1. Tremendous TDS Creep, meaning that water quality will be greatly diminished; and 2. Very high cost for membranes. In my opinion, it is just plain dumb to use a system with membranes that are designed to deliver 700 GPD for an application where 5-10 gallons per day are needed, whether it from the USA, Taiwan, or Egypt! Bacteria problems can still exist in tankless systems and if that is an issue, you can add an in-line UV for a lot less money.
January 11, 2011 at 11:34 AM
I've had a Merlin for 5 years and have been pretty happy with it. Our water is pretty mineral free to begin with but I like the peace of mind that RO provides. I do use it for beer brewing and cooking. Initially the unit did run continuously, but I called GE and they told me it was from the early filter designs. They sent me several replacement polishing filters and the issue went away. If I was buying a new system I would of course skip one that is discontinued and look for something else. The smaller RO tank systems however were never up to the task of giving me 20 gallons on brewday.
January 11, 2011 at 9:31 PM
Sam, Some people had success with the Merlin, but the failure rate was very high, which is why it was discontinued. A permeate pump RO with a 14 or 20 gallon tank and a 100 GPD membrane produces a phemonominal amount of water and pressure.
June 28, 2018 at 12:00 AM
You buy those 2.5 gallon empty jugs at the store run the Merlin for 5 mins then fill each uo and placed them in your refrigerator for use, Dumb Ass..
Mark Timmons
June 28, 2018 at 7:47 AM
The real Dumb Ass is the person who runs a Merlin for 5 minutes and thinks the water is good. Check it with a TDS meter and you will know who the Dumb Ass is. I won;t have to call you that... you will know! Cheers!